-LRB- CNN -RRB- -- Teachers -- like me -- love `` teachable moments , '' so here 's a big one from Monday 's sweeping Supreme Court decision on gun rights and the states , McDonald v. Chicago . In it , the court not only validated individual gun rights , but applied them to every state and locality in the country .

Americans know they have rights . Even some of my students who confess to near-total ignorance of American politics know they have free speech , the right to peaceably assemble , and the right to have a lawyer , should they run afoul of the law . But what none of my students know -- and what most Americans also do n't know -- is that we can lay claim to these and other sacred Bill of Rights freedoms because of a different constitutional amendment , a cluster of 20th-century court cases , and something called `` incorporation . ''

Early in America 's history , court rulings established that the Constitution 's Bill of Rights applied only to actions by the federal government , not the states . So , for example , if local police tried to shutter a newspaper for publishing legitimate , if unpopular , news , the newspaper would have to turn to that state 's constitution for protection or help , and not to the First Amendment 's protection of a free press .

And since every state constitution is different , the actual rights of citizens varied widely from state to state . Moreover , in the nation 's first century , citizens rarely had direct dealings with a national government of limited size and reach .

All this changed when the Fourteenth Amendment was added to the Constitution after the Civil War . Several decades later , the court concluded that the Fourteenth Amendment 's provision saying that states may not deprive persons of `` life , liberty , or property , without due process of law '' could now be used to apply or `` incorporate '' key provisions of the Bill of Rights to the states .

Note , however , that this process occurred selectively , provision by provision , and over seven decades . The first Bill of Rights protection to be applied to the states was in 1897 , when the Fifth Amendment 's guarantee that private property was not to be taken for public use `` without just compensation '' was incorporated . Following that , the court incorporated free speech in 1925 , press freedom in 1931 , free exercise of religion in 1934 , and so on until 1969 , when it applied the protection against double jeopardy -LRB- being tried for the same crime twice -RRB- to the states .

By design , this piecemeal process did n't include everything . -LRB- No one would argue that the Seventh Amendment 's unincorporated right to common law suits `` where the value in controversy shall exceed twenty dollars '' was the equivalent of free speech . -RRB- But most felt that incorporation was at an end , until two years ago .

In its landmark 2008 decision , D.C. v. Heller , the Supreme Court struck down the District of Columbia 's decades-old handgun ban as in violation of the Second Amendment 's right to bear arms .

This decision was momentous for two reasons . First , it was the first time in history that a gun law was struck down as a violation of the amendment . Second , the court contradicted past rulings that interpreted the amendment as pertaining only to citizen gun possession in connection with the `` well regulated militia '' mentioned in the first half of the amendment , and instead concluded that it protected an individual or personal right to own a handgun for protection in the home .

Because D.C. is a federal enclave , the Second Amendment could be brought to bear without addressing the fact that it had never been applied to the states -LRB- the high court has repeatedly refused to hear Second Amendment-based challenges in the past -RRB- .

This brings us to McDonald , in which gun rights advocates challenged Chicago 's local handgun ban as in violation of Heller -- but they also asked the court to now incorporate the Second Amendment . A five-member majority obliged . In his majority opinion , Justice Samuel Alito concluded that the individual right to bear arms , while subject to the limits outlined in Heller two years earlier that recognized most existing gun laws , was `` fundamental to our scheme of ordered liberty '' -- the litmus test for judging whether a right was important enough to be applied to the 50 states .

Readers eager to learn more about competing theories of incorporation are invited to plow through the five separate opinions that compose the case 's 214 page decision .

But whether one agrees with Justice Alito that the right to own handguns promotes ordered liberty because they are `` the most preferred firearm ... for protection of one 's home and family , '' or with Justice John Paul Stevens , who wrote in his dissent that guns in society `` destabilize ordered liberty '' by taking the lives of 30,000 Americans annually , Americans should at least know better today that the path to American rights runs through the Fourteenth Amendment .

The opinions expressed in this commentary are solely those of Robert J. Spitzer

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Spitzer : Court validated individual gun rights and applied them to every state , locality

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Court 's 2008 decision in D.C. v. Heller was momentous , Spitzer says

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The path to American rights runs through the Fourteenth Amendment , Spitzer says